javaweb登录注册拦截器数据库连接增删改查代码

好的，我为你提供一个简单的示例代码来实现JavaWeb登录注册功能、拦截器、数据库连接以及增删改查操作。请注意，以下代码仅供参考，你还需要根据具体需求和数据库配置进行适当修改。

1. 创建LoginServlet.java：

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        
        // 验证用户名和密码是否正确，这里省略具体实现
        
        if (验证成功) {
            request.getSession().setAttribute("username", username);
            response.sendRedirect("home.jsp"); // 登录成功后重定向到首页或其他页面
        } else {
            response.sendRedirect("login.jsp?error=1"); // 登录失败，重定向到登录页面并传递错误信息
        }
    }
}

2. 创建RegisterServlet.java：

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class RegisterServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        
        // 将用户名和密码保存到数据库，这里省略具体实现
        
        response.sendRedirect("login.jsp"); // 注册成功后重定向到登录页面
    }
}

3. 创建拦截器（Interceptor）LoginInterceptor.java：

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginInterceptor implements Filter {
    public void init(FilterConfig filterConfig) throws ServletException {
        // 初始化操作
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;
        
        String username = (String) request.getSession().getAttribute("username");
        
        if (username == null) {
            response.sendRedirect("login.jsp"); // 未登录，重定向到登录页面
        } else {
            chain.doFilter(request, response); // 已登录，继续执行后续操作
        }
    }

    public void destroy() {
        // 销毁操作
    }
}

4. 连接数据库和增删改查操作的示例代码：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class DBHelper {
    private static final String url = "jdbc:mysql://localhost:3306/database_name";
    private static final String username = "your_username";
    private static final String password = "your_password";
    
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url, username, password);
    }
    
    public static void closeConnection(Connection conn) {
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    
    // 插入操作示例
    public static void insertData(String username, String password) throws SQLException {
        Connection conn = null;
        PreparedStatement stmt = null;
        
        try {
            conn = getConnection();
            String sql = "INSERT INTO user (username, password) VALUES (?, ?)";
            stmt = conn.prepareStatement(sql);
            stmt.setString(1, username);
            stmt.setString(2, password);
            stmt.executeUpdate();
        } finally {
            if (stmt != null) {
                stmt.close();
            }
            closeConnection(conn);
        }
    }
    
    // 查询操作示例
    public static void queryData() throws SQLException {
        Connection conn = null;
        PreparedStatement stmt = null;
        ResultSet rs = null;
        
        try {
            conn = getConnection();
            String sql = "SELECT * FROM user";
            stmt = conn.prepareStatement(sql);
            rs = stmt.executeQuery();
            
            while (rs.next()) {
                String username = rs.getString("username");
                String password = rs.getString("password");
                System.out.println("Username: " + username + ", Password: " + password);
            }
        } finally {
            if (rs != null) {
                rs.close();
            }
            if (stmt != null) {
                stmt.close();
            }
            closeConnection(conn);
        }
    }
    
    // 其他的更新和删除操作类似，可以根据需要进行实现
}

以上是一个简单的示例代码，你可以根据需求进行适当调整和扩展。希望对你有所帮助！如果还有其他问题，请随时提问。